But he was the first scientist to correctly explain why the sea water is so blue. Look down and you will know why.
Raman (Sir Chandrasekhara Venkataraman, 1888 (Year of the Fifth Year)-1970). Indian physicist, also translated as Raman. Because of his research work on light scattering and the discovery of Raman effect, he won the 1930 Nobel Prize in physics. 1970 died at the age of 82.
1930 the nobel prize in physics was awarded to Raman of the university of Calcutta, India, in recognition of his research on light scattering and the discovery of the law named after him.
Raman is an Indian and the first Asian scientist to win the Nobel Prize in Physics. Raman is also an educator. He is engaged in postgraduate training and has sent many outstanding talents to many important positions in India.
Raman1888165438+10 was born in Ricino, southern India. My father is a professor of mathematics and physics at the university. He received science education from an early age and cultivated his interest in music and musical instruments.
He has outstanding talent. /kloc-graduated from university at the age of 0/6 and won the gold medal in physics with the first place. 19 years old, obtained a master's degree with honors. 1906, at the age of 18, he published a paper on the diffraction effect of light in the famous British scientific magazine Nature. Due to illness, Raman lost the opportunity to do a doctoral thesis in a famous British university. Before independence, India, if it didn't get a doctorate in Britain, meant that it was not qualified to work in the scientific and cultural circles. But at that time, the accounting industry was the only exception, and there was no need to go to the UK for training first. So Raman applied to the Ministry of Finance for a job, won the first place and was awarded the position of chief accounting assistant.
Raman has done a good job in the Ministry of Finance, and his responsibilities are getting heavier and heavier, but he doesn't want to immerse himself in officialdom. He stuck to his scientific goals and spent all his spare time continuing to study acoustics and musical instrument theory. In Kolkata, there is an academic institution called Indian Association for Science Education, which has a laboratory where Raman conducts his acoustic and optical research. After ten years of hard work, Raman has made a series of achievements and published many papers without the guidance of senior researchers.
19 17 the university of Calcutta made an exception and invited him as a professor of physics, so that he could concentrate on scientific research from now on. During the 16 years of teaching at the University of Calcutta, he still conducted experiments at the Indian Association for Science Education. Students, teachers and visiting scholars all came here to learn from him and cooperate with him, and gradually formed an academic group with him as the core. Encouraged by his example and achievements, many people embarked on the road of scientific research. Among them, there are famous physicists M.N. Saha and S.N. Bose. At this time, Kolkata was setting up an Indian research center, and the University of Kolkata and Raman Group became the core of popular support. 192 1 year, Raman gave a lecture in Britain on behalf of the University of Calcutta, which showed that their achievements were internationally recognized.
1934, Raman and other scholars founded the Indian Academy of Sciences and personally served as the president. 1947, Raman Institute was established. He has made great achievements in the development of science in India. Raman has a good eye for the theme of molecular scattering. In his continuous efforts for many years, there is obviously an idea, that is, to persistently carry out basic research in view of the weak links in theory. Raman attaches great importance to discovering talents. From the Indian Association for Science Education to the Raman Institute, he is always surrounded by groups of talented students and collaborators. According to the statistics of light scattering, in the middle of thirty years, 66 scholars published 377 papers in his laboratory. He seduced students and was deeply admired and loved by them. Raman likes music, flowers and rocks. He studied the structure of diamonds and spent most of his prize money. In his later years, he devoted himself to the spectral analysis of flowers. On his 80th birthday, he published his album Visual Physiology. Raman loves roses more than anything else. He owns a rose garden. Raman died in 1970 at the age of 82 and was cremated in his garden according to his wishes.
After the Compton effect of X-rays was discovered, Heisenberg predicted in 1925 that visible light would have a similar effect. 1928, Raman pointed out in the article "A New Radiation" that when monochromatic light directionally passes through transparent materials, some light will be scattered. The spectrum of scattered light contains not only some original wavelength light, but also some weak light, and its wavelength is different from the original wavelength by a constant. This phenomenon that the frequency of monochromatic light changes after being scattered by medium molecules is called combined scattering effect, also known as Raman effect. This discovery was quickly recognized. The Royal Society officially called it "one of the three or four most outstanding discoveries in experimental physics in the 1920s".
Raman effect provides new evidence for the quantum theory of light. When monochromatic light with frequency ν0 is incident on the medium, two kinds of scattering processes will occur at the same time: one is the scattering with constant frequency (ν=ν0), that is, Rayleigh scattering, which is caused by the elastic collision between incident light quantum and scattering molecules; The other is frequency-dependent Raman scattering (ν = ν 0 νR), where νR is called Raman frequency. The change of scattered light frequency is due to the energy exchange between incident light quantum and scattering molecules, and the exchanged energy (hνR) is determined by the vibration or rotation energy level of scattering molecules. Later studies show that Raman effect is very important for studying molecular structure and chemical analysis.
How was the Raman effect discovered?
Raman scattering, also known as Raman scattering, was discovered by Indian physicist Raman in 1928, which refers to the phenomenon that the frequency of light waves changes after being scattered. 1930 the nobel prize in physics was awarded to sir Chandrasekhara Venkata Raman (1888-1970), who was then working at the university of Calcutta, India, in recognition of his research on light scattering and his discovery of the law named after him.
There is a special effect in light scattering, which is similar to Compton effect of X-ray scattering. The frequency of light will change after scattering. The change of frequency depends on the characteristics of scattering matter. This is the Raman effect, which was discovered by 1928 Raman in the process of studying light scattering. A few months after Raman and his collaborators announced the discovery of this effect, Landsberg and L Mandelstam of the Soviet Union also independently discovered this effect, which they called joint scattering. Raman spectrum is the result of the superposition of the vibrational energy or rotational energy of the molecule and the photon energy when the incident photon collides with the molecule. Using Raman spectroscopy, the molecular energy spectrum in infrared region can be transferred to visible region for observation. Therefore, Raman spectroscopy, as a supplement to infrared spectroscopy, is a powerful weapon to study molecular structure.
192 1 in the summer of, an Indian scholar was bending over the deck to observe the sea surface with simple optical instruments on the passenger ship S.S.Narkunda sailing in the Mediterranean. He was fascinated by the deep blue of the sea water and was determined to investigate the source of the color of the sea water. This Indian scholar is Raman. He is on his way to Britain, representing the University of Calcutta, the highest institution in India, attending the Commonwealth University Conference in Oxford, and preparing to give a speech at the Royal Society. He was only 33 years old at this time. For Raman, the blue of the sea is not unusual. University of madras, where he goes to school, faces the Bay of Bengal, and he can see the changing colors of the sea every day. In fact, as early as 16 years old (1904), he was already familiar with the famous physicist Rui's explanation of blue sky by using the law that the intensity of scattered light in molecular scattering is inversely proportional to the fourth power of wavelength (also called Rayleigh's law). I don't know if it's because of my character of exploring the mysteries of nature, or because of my in-depth thinking of consulting literature when studying light scattering. He noticed that a passage of Rayleigh was debatable. Rayleigh said: "The blue of the deep sea is not the color of the sea, but the blue of the sky is reflected by the sea." Rayleigh's exposition of seawater blue has always been Raman's concern. He is determined to make a field trip. So, when Raman set out for England, he prepared a set of experimental devices in his luggage: several Nicole prisms, small telescopes, slits and even a grating. Both ends of the telescope are equipped with Nicole prisms as polarizers and analyzers, which can be used for experiments at any time. He used a Nicole prism to observe the reflected light of seawater along Brewster's angle, thus eliminating the blue light from the sky. The light seen in this way should be the color of the sea itself. So what you see from here is a deeper blue than the sky. He also used grating to analyze the color of seawater and found that the maximum value of seawater spectrum was bluer than the maximum value of sky spectrum. It can be seen that the color of seawater is not caused by the color of the sky, but an attribute of seawater itself. Raman believes that this must be due to the scattering of light by water molecules. He wrote two papers on the ship back home to discuss this phenomenon. These documents were sent to England during the stopover and published in two magazines in London.
After Raman returned to India, he immediately conducted a series of experiments and theoretical studies in the Science Education Association to explore the scattering law of light in various transparent media. Many people took part in these studies. These people are mostly school teachers. They came to the Science Education Association on holidays and conducted light scattering or other experiments with Raman's company or guidance, which played a positive role in Raman's research. In seven years, they published about fifty or sixty papers. At first, they studied the scattering law of molecules in various media, chose different molecular structures, different states of matter, different pressures and temperatures, and even conducted scattering experiments at critical point phase transition. 1922, Raman wrote a pamphlet summarizing this research, entitled "Molecular Diffraction of Light", which systematically expounded his views. In the last chapter, he mentioned using quantum theory to analyze scattering phenomenon, and thought that it was possible to distinguish classical electromagnetic theory from light quantum through further experiments. 1923 In April, one of his students, K.R.Ramanathan, first observed the phenomenon of color change in light scattering. The experiment uses the sun as the light source, illuminates the flask filled with pure water or pure alcohol through the purple filter, and then observes it from the side, but unexpectedly observes a very weak green component. Ramanasan doesn't understand this phenomenon, and thinks it is secondary radiation caused by impurities, similar to fluorescence. Therefore, it is called "weak fluorescence" in the paper. However, Raman does not think that this is a phenomenon caused by impurities. If it is really the fluorescence of impurities, this effect should be eliminated in carefully purified samples.
In the next two years, K.S. Clichy, another student of Raman, observed the scattered light of 65 kinds of purified liquids and proved that they all had similar "weak fluorescence". He also found that the scattered light with color change was partially polarized. As we all know, fluorescence is a kind of natural light without polarization. This proves that this phenomenon of wavelength change is not a fluorescence effect.
Raman and his students thought of many ways to study this phenomenon. They tried to photograph scattered light for comparison, but failed. They used complementary filters, eyepieces of large telescopes and short-focus lenses to focus on the sun, and the test samples expanded from liquid to solid, insisting on various experiments.
At the same time, Raman is also pursuing a theoretical explanation. 1924 Raman's visit to the United States coincided with A.H. Compton's recent discovery of the effect of wavelength lengthening after X-ray scattering, and skeptics were stirring up controversy. Raman obviously got important enlightenment from Compton's discovery, and later he regarded his discovery as "the optical counterpart of Compton effect". Raman also experienced twists and turns similar to Compton. After six or seven years of exploration, a clear conclusion was reached at the beginning of 1928. At this time, Raman has realized that the weak polarized scattered light with color change is a common phenomenon. Referring to the name "change line" in Compton effect, he called this new radiation "modified scattering". Raman further improved the filtering method, adding a piece of uranium glass in front of the blue-violet filter, so that the incident sunlight can only pass through a narrower band, and then observing the scattered light with a visible spectroscope, it is found that there is a dark area between the variable scattering and the constant incident light.
1928 On the afternoon of February 28th, Raman decided to use monochromatic light as the light source and made a very beautiful and decisive experiment. He looked at the scattered light of the visual beam splitter and found that there were more than two sharp bright lines in the blue and green areas. Each incident spectral line has a corresponding variable scattering line. In general, the frequency of variable scattering lines is lower than that of incident light, and occasionally scattered lines with higher frequency than incident light are observed, but the intensity is weak.
Soon, people began to call this newly discovered phenomenon Raman effect. 1930, American spectrologist R.W.Wood named the variable scattering line with lower frequency as Stokes line. Anti-Stokes spectral lines with higher frequency.
The news that Raman discovered abnormal scattering spread all over the world, causing strong repercussions, and many laboratories repeated it one after another, confirming and developing his achievements. 1928 published 57 papers on Raman effect. The scientific community spoke highly of his discovery. Raman is the pride of the Indian people and sets an example for scientists in the third world. It is admirable that India, where he lived for most of his life before independence, has made such outstanding achievements. Raman, in particular, is a scientist trained in India. He has always been based in India, worked hard, established a distinctive scientific research center, and walked to the forefront of the world.